Piezoelectric blade blowers are known which are much smaller than the smallest rotary fans and are used to cool electronic equipment. These blowers are highly efficient, have long life, generate little noise or magnetic interference and are approximately two inches by one inch by three quarters of an inch in size. However, they too have drawbacks. They are not small enough for direct mounting on printed circuit boards and they require a 115-volt, 60-line current, which introduces 60 Hz magnetic noise in the circuit boards as well as requiring that a 115-volt source be made available at the board. Attempts to use a piezoelectric crystal directly to pump air by acoustic streaming have also been less than successful because large crystals are required which are difficult and expensive to obtain in production. Acoustic streaming results from the fact that air accelerated by an oscillating surface does not reverse its direction when the surface does, due to inertia and compressibility, further complicated at higher amplitudes by turbulence and vortex formation.